1. Field of the Invention
The present invention relates to water heaters, and more particularly to a “tankless” water heater with an electrically powered heating element and a relatively small tank for substantially instantaneous heating of the water.
2. Description of the Related Art
Various types of tankless water heaters have been devised over the years, including water heaters with electrically powered heating elements in a plastic housing. Tankless water heaters have frequently been directed to point of use, meaning the water heater was placed immediately upstream from a heated water use device, such as a sink or a shower.
Several tankless water heater manufacturers provide multiple water housings, which may be plumbed in parallel and/or in series. Another manufacturer employs a single metal tank for receiving the electrically powered heater. The water inlet to the one or more housings and the water outlet from the one or more housings typically have reduced diameters of ⅜ inch tubing. This restricted tubing in part tends to create a high fluid velocity in portions of the tank to entrain air bubbles in the fluid passing to the outlet, thereby attempting to avoid undesirable air pockets within the housing chamber. Moreover, restricted inlets and outlets create a high pressure drop such that the unit may not be suitable for various applications. Water outlets from many heaters extend from the bottom of the tank housing.
Prior art tankless water heaters have disadvantages in that the mounting orientation of the water heater is limited; most heaters must be mounted with the central tank axis vertical. Many prior art tankless water heaters subject the user to a scalding condition when latent heat after shut-down causes water hotter than desired to remain in the housing chamber after the heater is shut off. After shut off, water temperature continues to increase in the housing due to the heated surroundings and the still hot heating element, and overheated hot water is subsequently released when the same or another user turns the water back on. Other tankless water heaters contain very little water, and the second user of the water does not benefit from the stored quantity of water in the heater after the first use is completed. Still other tankless water heaters use expensive flow control sensors or do not accurately detect a “flow” condition, thereby minimizing the effective control of heat to the water. Some tankless water heaters incorporate mixing valves to mix hot water discharged from the heater, thereby creating another expense to the user.
Prior art patents include U.S. Pat. Nos. 5,216,743, 7,616,873, 5,866,880, 6,080,971, and 6,246,831. U.S. Pat. Nos. 5,216,743, 5,866,880, 6,080,971, 6,246,831, and 7,616,873 disclose tankless water heaters with a plastic housing and improved heater controls. U.S. Pat. Nos. 6,909,843, 7,567,751 and 7,779,790 disclose a single chamber heater with one or more heating elements therein.
The disadvantages of the prior art are overcome by the present invention, an improved tankless water heater is hereinafter disclosed.